Fabrication of a structural member or workpiece (such as, for example, a structural steel I-beam, wide flange H-beam, angle, channel, flat plate, etc.) may require processing such as cutting, drilling, punching, scribing or marking, and/or shearing portions of the workpiece. Conventional and specialized processing machines perform these processing operations. For example, a processing machine can be used to drill holes in a workpiece.
In one type of processing line or layout, one or more workpieces are supported lengthwise on a series of storage tables or transfer stands that are located adjacent to a main conveyor, where the workpieces are loaded or conveyed onto the main conveyor, which leads to, and away from, one or more processing machines. The main conveyor has, for example, been an elevated structure having chain-driven rollers that define a conveying path and are capable of supporting and conveying the workpiece along a desired path. In order to accurately determine the location of the workpiece as it is conveyed relative to a processing machine, devices have been used to measure the length of the workpiece that has been indexed (i.e., moved) into or through the machine along an X-axis. For example, measuring devices have used a wheel biased in the Z direction against a measured workpiece surface maintained in an X-Y plane (normal to the Z direction, with the wheel rolling on the measured workpiece surface. A rotational sensor or shaft encoder has measured the rotational movement of the wheel which data is converted by a processor or control system of the processing machine into the distance travelled by the workpiece along the X-axis.
For example, FIGS. 1 and 2 illustrate a prior art processing machine 100 for punching, shearing, and marking, sold under the name AngleMaster, designated as model no. AFPS-643/Q by Peddinghaus Corporation, having offices at 300 N Washington Ave, Bradley, Ill. 60915. This processing machine is especially suitable for use with large mass or heavy workpieces and includes a prior art measuring device 400 especially suitable for use with large mass or heavy workpieces (e.g., large structural supports such as wide-flange H-beams, I-beams, C-beams, or angles, channels for use in building construction). The weight per unit length of a very heavy wide flange H-beam processed in the United States of America may, for example, exceed about 1,100 kg/m.
The processing machine 100 includes, inter alia, a measuring device 400 having a wheel 410 which rolls along a surface 108 of a workpiece 116 moved in the X axis direction (FIGS. 3 and 4). For clarity of description and orientation, the surface 108 lies in the X-Y plane of an orthogonal space having X-Y-Z axes, with measurement being of workpiece movement in the X direction. Thus, it should be appreciated that the wheel 410 of the device 400 rotates around a rotational axis “RPA” which is spaced from the surface 108 in the Z direction and is substantially parallel to the Y axis. It should also be appreciated that in addition to the illustrated machine 100, such measuring devices 400 have and can also be used with other processing machines for punching, drilling, cutting, welding, marking, etc. one or more workpieces, or other machines for handling materials having a surface to be measured.
A workpiece 116 in the form of an angle is shown in FIGS. 1-2 resting on several rollers 118 at the inlet side 120 of the processing machine 100, prior to processing of the workpiece 116. The measuring device 400 is shown affixed to the inlet side 120 of the processing machine 100, and additional measuring devices (not shown in the drawings) have also been included (e.g., affixed toward an outlet side 122 of the processing machine 100) with the illustrated and other processing machines. When the workpiece 116 is moved or conveyed from the initial position shown in FIG. 2 into the processing machine 100, the workpiece 116 will be hydraulically clamped by the processing machine 100 against one or more datum rollers or surfaces so as to locate the workpiece 116 in a known position relative to the processing machine 100. Additionally, one or more suitable edge detecting sensors of the machine may be used to locate the forward or leading edge of the workpiece 116, whereupon with the workpiece 116 clamped in this known position against the datum, the measurement device wheel 410 that rolls along the surface 108 of the workpiece 116, where rotation of the wheel 410 is monitored to determine movement and positioning of the workpiece 116 in the X-direction.
The prior art measuring device wheel 410 has a plurality of circumferentially spaced radial teeth 414 which make contact with the X-Y surface 108 of the workpiece 116. When the dimensions of the wheel 410 are known and the wheel 410 rolls without slipping on the workpiece surface 108, proper measurements may be taken. However, undesirable relative movement (e.g., rotation or translation which could be caused by material imperfections of the workpiece 116 or forces imparted on the workpiece 116 during processing) are sometimes encountered between the workpiece 116 and the wheel 410. Such undesirable relative movement and forces can damage the wheel 410. For example, uneven or angled rolling of the teeth 414 relative to the workpiece surface 108 can result in forces in the Y direction, leading to undesirable wear and/or warping which can essentially change the dimensions of the wheel 410. For example, the measuring wheel 410 having the configuration as shown in FIG. 5 can have its teeth 414 worn down unevenly (FIG. 6A) and/or can be worn warped in a single direction (FIG. 6B) or in multiple directions like a potato chip (FIG. 6C). Such distortions of the measuring wheel 410 can result in inaccurate recording of the movement of the workpiece 116, whether from distortions in the wheel 410 itself or from failure to make proper rolling contact between the workpiece 116 and the wheel 410.
The present invention is directed toward overcoming one or more of the problems discussed above.